It is known that the compound A has an excellent gonadotropin releasing hormone (GnRH) receptor antagonistic action and is useful as a therapeutic agent for gonadotropin-dependent diseases (for example, prostate cancer, breast cancer, endometriosis, uterine fibroid, prostatic hyperplasia, or the like) (Patent Document 1).
In Patent Document 1, the compound A is disclosed in Example 726 and it is described that the compound A is produced by the same method as the compound of Example 696. Here, it is described that the compound of Example 696 is produced by subjecting (2R)-2-hydroxypropanimidamide hydrochloride to a sulfonyl amidination reaction with 5-[2-(1,3-dihydro-2H-benzoimidazol-2-ylidene)-3-(3-fluorophenyl)-3-oxopropanoyl]-2-fluorobenzenesulfonyl chloride in the presence of sodium hydride, in tetrahydrofuran, followed by a liquid separation operation and purification with columns. However, this production method requires purification with columns so as to remove the impurities and thus, it has been desired to establish a production method for obtaining a compound A at a high purity, which is suitable for industrial production, without carrying out purification with columns.